1. Technical Field
This invention generally relates to pusher furnaces. More particularly, the invention relates to a pusher plate for use in carrying materials through a pusher furnace. Specifically, the invention relates to a pusher plate that includes a guidance system for controlling the lateral motion of the plate relative to the axis of travel and thereby increases the tendency of the pusher plate to move smoothly through the furnace.
2. Background Information
Pusher furnaces are designed in various lengths and may contain multiple heating and cooling sections as required by the application. These furnaces also include a substantially continuous flat surface or a pair of slide rails running through the interior thereof. A plurality of pusher plates are pushed sequentially along the flat surface or slide rails and through the line of heating sections. So, for example, a first pusher plate is placed on the slide rails and is pushed into the first heating section by a pusher arm or other suitable mechanism. A second pusher plate is then positioned behind the first pusher plate and the pusher arm forces the leading face of the second plate into abutting contact with the trailing face of the first pusher plate. The pusher arm then pushes the second plate into the opening in the first heating section. This motion advances the position of the first pusher plate within the first heating section. A third pusher plate is then introduced behind the second pusher plate and the arm pushes that third plate into contact with the trailing face of the second pusher plate, thereby changing the second and first pusher plates positions within the heating section and so on.
The materials to be processed in the pusher furnace are placed onto the upper surface of the pusher plates. Typical materials processed in this manner include various materials required for electronic or ceramic components, as well as different metals that are to be annealed, sintered or de-waxed. Each of the heating sections in the furnace is set up to produce slightly different, but very specific, heating conditions. As the pusher plates move through the furnace, they pass through each of these different specific environments and are thereby progressively processed.
One of the main problems experienced in pusher furnace systems is that even small variations in the dimensions of the pusher plates can cause the leading and trailing faces of the plates to meet unevenly. This may cause the plates to twist or turn slightly on the slide rails and may result in the plates bumping into the side walls of the heating section, rising up over an adjacent plate or being pushed under an adjacent plate. Furthermore, the plates may become jammed or wedged against each other or against the heating section walls. This can result in physical damage to the plates, to the heating section walls or to the material carried on the plates. Furthermore, damage may also result to the plates themselves from mechanical stresses due to uneven contact between adjacent plate contact surfaces.
There is therefore a need in the art for an improved pusher plate for use in continuous or indexing pusher furnaces which tends to stay in line when pushed, tends not to rise up over the plates in front of it and which reduces the potential for stoppage of the line during processing.